Question

Find out percentage purity of impure sample of oxalic acid

Answer 1

Answer:

Indicator

KMnO4 is a self-indicator.

End Point

Colourless to permanent pink colour (KMnO4 in burette).

Procedure

Weigh exactly 2.0 g of oxalic acid and dissolve in water to prepare 500 ml of its solution using a 500 ml measuring flask. Rinse the pipette with the oxalic acid solution and pipette out 20 ml of it in a washed titration flask.

Rinse and fill the burette with M/100 KMnO4 solution.

 

Add one test-tube (~ 20 ml) full of dilute sulphuric acid (~ 2 M) to the solution in titration flask.

Note the initial reading of the burette.

Heat the flask to 60-70°C and add KMnO4 solution from the burette till a permanent light pink colour just appears in the solution in the titration flask.

Note the final reading of the burette.

Repeat the above steps 4-5 times to get a set of three concordant readings.

Observations

Weight of watch glass =……. g

Weight of watch glass + Mohr’s salt =…………..g

Weight of Mohr’s salt = 2.00 g

Volume of Mohr’s salt solution prepared = 500 ml

Solution taken in burette = M/100 KMnO4

Volume of Mohr’s salt solution taken for each titration = 20.0 ml

Calculations

a) molarity of the KMnO4 solution

from the overall balanced chemical equation it's clear that 2 moles of  KMnO4  react with 5 moles of oxalic  acid

hope it helps u ...........have a good day